Modulator for sound-producing machines.



. J; c. DRAKE. v MODULATOR FOR SOUND PRODUCING MACHINES. APPLICATION FIL'ED was 6. me. I 1,254,665. Y I Patented Jan. 29,1918.

I 2 SHEETS-SHEET l- 4 1. cJuRAKE, MODULATOR FDR SOUND PRODUCING MACHINES- Amicm'qu mm JUNE 6. I9l6.

Patented Jan. 29,1918,

2 SHEETS-SHEET 2.

- UNITED STATES PATENT OFFICE.

JAMES C. DRAKE, OF ROCHESTER, MINNESOTA, ASSIGN OR TO SEARS, BOEBUCK & COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

MODULATOR FOB. SOUND-PRODUCING MACHINES.

Patented Jan.29, 1918.

- "Application filed June 6, 1916. Serial No. 101,909.

To all whom it may concern:

Be it known that I, JAMES C. DRAKE, a citizen of the United States, residing at Rochester,,in the county of Olmstead, State of Minnesota, have invented certain new and useful Improvements in Modulators for Sound-Producing Machines, of which the following is .a specification, reference being had therein to the accompanying drawing.

My invention relates to means for regulating the volume of sound transmitted througha conveyer or horn such for example as those employed in connection with talking machines, and has for its object the provision of -means whereby the volume-of sound may be varied from the full capacity of the conveyer-or horn, down to a very low and soft tone, without reflection, interference, false vibration's,-or any alteration or deterioration inthe timbre or quality of the tone.

Ancillary objects of the invention are, to enable the device to be easily and conveniently controlled by an operator, to provide convenient and efficient means for looking the device in difierent positions, and to reduce the entire structure to a simple but highly efficient mechanical combination easily installed, but not easily deranged.

I attain my principal object by providing an inverted padded cone after the fashion of a mute movable with respect to a seat formed in the sound .conveyer or horn so that in one position the cone will close the sound conveying channel, in its extreme opposite position will widely open the same, and in its intermediate positions will progressively decrease the area of said channel from the open or maximum position to the minimum or closed position.

I attain my ancillary objects by mounting the cone modulator on one end of, .a rocking lever Whose transverse shaft extends out through an opening in the side of the horn and has its end fitted with means such as a crank handle, whereby it may be turned into various positions, corresponding to the several positions which the modulator. is desired to assume; by providing an arc plate in connection with the crank handle with means for locking the same thereto; and by mounting the modulator by means of a flexible joint directly upon the end of the rocking lever in the horn, securing said lever directly upon the transverse control shaft, and by extending said shaft directly to a point within reach of the operator. Incidentally I preferably provide the shaft with means such as a spring for the purpose of normally maintaining the modulator in one extreme ,position or the other.

It should be understood in reading the following detailed description, first that the invention is applicable to various sound producing devices, including phonographs, loud talking telephones, some types of megaphones, automatic and other musical instru-j ments, etc., and furthermore, the description and illustration of species hereinafter," are given for purposes of definition and notof limitation. It is to be understood that subordinate details and non-essential features may be altered and modified without departing from the spirit of my invention.

My invention is illustrated in the accompanying drawings, in which: I

Figure 1 is a vertical sectional view showing my modulator and its operating parts applied to the horn of a phonograph.

Fig. 2 is a vertical section view taken at right angles to Fig. 1.

Fig. 3 is aface view of the lockingineans for the operating shaft,

Figs. 4 and 5 are respectively a plan view and a transverse section, both .on an enlarged scale, of the knob on the crank arm and itslocking means. A

Fig. 6 is a view similar to Fig. 2 showing the modulator worked by a bell crank by means of a cord or cable operated from a distance.

Fig. 7 is a view similar to Fig. 6

"this term comprehends any form of conveyer without limitation.

The horn 2.1s prov ded with an annular seat 3, somewhat slmllar to an ordinary offbut taken in a plane at right angles to the plane lar opening,18 in the arm. Through these the arc of travel -of--the stem (see Figs. 1,

set valve. seat. From this seat the horn drops and then bends forwardly as clearly shown in Fig. 2, terminating in an expanded or flared end, or such other form of opening as may be desired. In the ordi-' nary talking machine or phonograph, with a concealed or cabineted horn of the type shown, the latter would be of cast iron from the motor part down to the bend, and usually of wood or the equivalent with stant ratio of enlargement or flare, to the opening in the side of the cabinet. For simplicity I have avoided showing details of the horn in the drawings, and in any case, my modulator, as a matter of convenience and expediency would be located as shown in the upper or metal part of the horn or conveyer.

The modulator itself is composed essentially of a thin metal hollow cone 4, heavily padded inside and out with material 5 such as felt adapted to absorb sound waves and thereby protect the cone and prevent forced vibrations of the metal therein. As a further means of absorbing sound waves, I provide a felt cap 6, which is stretched over and permanently fixed to the large end of the cone 4. In order to work this modulator, I provide a rock-shaft 7, journaled transversely at 8 in one side of the horn 2, and at 9 in an opening through the wall of the cabinet 10, which is shown only in fragmentary form in Figs. 1 and 6. At its outer end the shaft carries a crank arm 11 rocked, describes an are over the plate 12. The shaft is preferably provided with means such as a coil spring 13 one end of which at 14 is fastened to the side of the cabinet, and the other end at 15 attached to the shaft, to exert a constant torque thereon, in the direction of its closing movement. In order to maintain the shaft however, in any position to which it may be set, the crank arm 11 is provided with locking means best shown in Figs. 3, 4 and 5. Upon the end of the arm 11 is provided a raised plate 16, having an opening 17 registering with a simiopeningspass'es the stem 22 of a button or knob 19, provided with aradial stud 20 which locks the stem on the knob either in depressed or elevatedposition and for that purpose may be raised and lowered through a notch 21 to oneside of the stud-opening 18 in the arm. Beneath I the arm, and in 22 of the knob, are openings 23, in the arc plate 12. By turning the knob so as to bring the stud 20 above the notch'21 and then turning the crank arm until the stem 22 registers with any'desired one of these openings 23, the knob may be pressed down until its end projects through the openlngs 23 as shown in Fig. 5, and by then giving it a partial turn 2 and 3) which, as the shaft is -when the cord is pulled out it the stud 20 will'pass beneath the solidportion of the arm 11 and lockthe parts against displacement.

Motion is communicated from the shaft 7 to the cone 4 by means of a rock lever 24, which is best shown in Fig. 2, although it may be seen foreshortened in Fig. 1. The end of this lever 24 has a pivotal connection 25with a socket piece 26 carrying a projecting stud 27, upon which is secured a short, flexible shaft or connector 28, the upper end of which takes. around a projecting stud 29 on the small end of the cone. The flexible shaft or connector 28 may be an ordinary tightly wound and stiff helical spring, soldered at its upper andlower ends to the two studs 29 and 27 respectively.

In Fig. 6 I have shown a modified form of mechanical motion for the modulator, the lever 24 in this case being a bellecrank lever, secured on the shaft 7, and having a cord or cable 30 secured to its upper end and extending out through an opening 31, in the side of the cabinet 10. i

The shaft 7, being provided with a helical spring to turn it constantly into open position, it is obvious that the modulator may be more or less closed by merely pulling upon the cord 30. I preferably provide the cord with a terminal knob or handle 32, which when the cord is retracted within the cabinet and not in use, will close the orifice 31 which may be provided with anydesired form of spring-clip or retaining means for holding the knob in position. The interior of the cabinet may also be fitted with a spring drum or other means for winding up the cord when not in use. In fact, such a spring drum may replace the upper arm 33 of the bell crank lever, being mounted on the shaft 7 to one end of which the spring should be secured, (the other end being secured to the outside of the drum), so that will turn the drum without affecting the modulator, but when the drum has turned to a predetermined limit stop, on the shaft 7, it will then resist further unwinding, and a continued pull will turn the shaft 7 and move the modulator. Conversely, when the pull on the cord is relaxed, the modulator will first assume its normal position, shown in full lines in Fig. 6,'and then the drum will start to rewind the cord. In this the spring on the drum must be of strength than the spring on the modulator shaft,'for'obvious reasons.

arrangement,

1 'Even though the cord or cable of Fig. .6

other words, in Figs. 6 and 7 the spring I3 I less is thought the operation and principles involved will require only brief mention. Those experienced in this art know that the devices heretofore employed and proposed for regulating the sound in talking machines reflect more or less of the sound waves back to the sound box, thus causing a buzz which is more or less apparent according to the density of the reflecting surface. If the interposed valve or muting member is too porous, the volume of sound will never be reduced to a desired minimum. In the present case with my invention, there is no refiection, and the sound at all times and in all stages of reduction, goes down into a very soft rich tone. The intensity or amplitude of the vibrations entering the neck of the horn 2 is lessened by their passage through the felt cap 6 of the modulator, inside of which they come in contact with the in-- Wardly tapering padded walls of the cone 4. By reason of-the taper there is no surface operating to reflect the sound 'waves directly back to the sound box, and with respect to such sound waves as are ultimately reflected out of the cone, the energy of their vibrations has then become so attenuated by conversion into heat through friction and viscosity that they become practically lost in the upper sound conveyer or tone arm and never reach the sound box.

When the modulator is seated firmly in the neck of the horn as shown in full lines in Figs. 1 and 2, the volume of transmitted sound is reduced to a minimum, and as the shaft 7 is turned, the lever 24: turns down the cone l gradually, and the sound gradually increases until the parts finally reach the position shown in Fig. 2, whenall the sound waves entering the horn are permitted to pass on and be reflected therein, thus obto Y taming the maximum volume according the design of the horn. Forpractical purposes, the positions of the modulator and its controlling parts may be limited to three, indicated on the arc plate of 'Fig. 3 by the legends soft, .medium and loud; but of course the number of these may be increased arZ Zibz'tum.

The function of the flexible joint 28 is dual; in the first place it permits a long swing of the lever 24, so as to bring its pivotal end 25 into the axial line of the upper opening 6 of the horn, which would otherwise be impossible on account of the shape and proportions of the modulator; and second, it compensates for any cumulative errors that may occur in manufacturing, so that the cone of the modulator when assema bled with the horn, will always be permitted to assume a central location.

Having thus described my invention what I claim and desire to secure by Letters Patent is:

1. In a sound producing device. a passageway having a sound receiving opening, and a modulator fitted to said opening comprising the following instrumentalities: a hollow conical body with its large end fitted to the opening and its smallend pointed in the direction of transmission of the sound, and means extending through the side of the passageway for moving said body to and from the opening.

2. In apparatus of the class described, a

sound opening, a conduit extending from said opening, and a modulator fitted to said conduit comprising the following instrumentalities; a transverse rock shaft extending through a wall of the conduit, a lever on said rock shaft, a non-resonant body tapering from one end to the other, with its larger end adapted in one position to close and in other positions to partially or completely open the conduit or passageway, a resilient connection between the small end of said body and the end of the rock shaft arranged to positively transmit motion therebetween in both operative movements, and means outside the conduit to move said shaft.

3. In apparatus of the class described, a sound opening, a conduit extending from said opening, and a modulator fitted to said conduit comprising the following in- .strumentalities; a transverse rock shaft ex- In testimony whereof I aflix my signature.-

JAMES C. DRAKE. 

